Our overall goal is to understand the mechanisms that determine how cells and tissues respond to implanted materials in order to improve the function of devices and combination products used clinically. Studies using titanium (Ti) substrates suggest that by understanding how surface morphology and chemistry modulate cell response, it may be possible to develop materials that control cell behavior through structural signaling, without the need for pharmacologic modification. The purpose of the present proposal is to use structured material surfaces to define which micron-scale and sub-micron scale topographical features regulate specific cell responses and to understand the underlying mechanisms involved. By controlling surface chemistry, we will also investigate how microarchitecture and hydrophilicity interact to control cell behavior. Our long term goal is to create rational biomimetic implants that facilitate normal tissue regeneration and repair. Our experimental hypothesis is that the physical and chemical properties of a surface determine integrin expression, influencing cellular signaling and response to factors that regulate osteogenesis, such as 1,25- dihydroxy vitamin D3 [1,25(OH)2D3] and estrogen. We will examine osteoblast behavior on defined Ti surfaces prepared using electochemical micromachining to produce micrometer scale structural features;submicron scale topography will be superimposed by chemically etching the surface under controlled conditions. Substrates will be designed that have comparable microarchitecture but different hydrophilicity. Cell culture models include: human osteoblast-like MG63 cells, normal human osteoblasts (NHOst cells), and the rat osteoblast-like cell line ROS 17/2.8. Three specific aims are proposed: Aim I. Examine the role of integrins in mediating the differential effects of surface design features on osteoblast phenotypic expression. Aim II. Examine the role of substrate architecture in the response of osteoblasts to 1,25(OH)2D3 and 17b- estradiol. Aim III. Examine the role of integrin-signaling in mediating the synergistic effect of surface design and steroid hormone action on osteoblast phenotypic expression. Thus, while our experiments are basic in nature, our intent is to conduct them in such a manner that the results can be applied to clinical implantology and tissue engineering.